Patent GB-599913-A (GB)
Title: Improvements in or relating to cathode ray tube inductors
IPC: G01S13/42
Filed: 1944-08-29
Abstract: 599,913. Radiolocation; saw-tooth generating circuits. SPERRY GYROSCOPE CO., Inc. Aug. 29, 1944, No. 16437. Convention date, Aug. 16, 1943. [Class 40 (v)] [Also in Group XXXVI] In a cathode-ray tube indicator system, suitable for use as an azimuth- or elevationtracking indicator, D.C. voltages are converted into sweep voltage for application to the cathode-ray tube deflecting plates by means of clamping circuits triggered by a pulse waveform. In the radiolocation system of Fig. 1, a beam 13 produced by a reflector 12 is scanned conically by rotation of the reflector by means of a motor 17. Signals reflected from an object 11 are fed to a receiver 19 and spin-frequency modulation due to misalignment between the object and the axis of rotation 15 is filtered out and fed to phase-sensitive detectors 21, 22 where it is compared with voltages from a twophase generator 18 on the motor shaft, to produce voltages representative of the azimuth and elevation errors. The error voltages are fed to azimuth and elevation indicator circuits 23, 24 together with a voltage from the A.V.C. circuit of the receiver over line 20 and a triggering voltage from a blocking oscillator 25. The indicator circuits produce radial-line presentation on the cathode-ray tubes 26, 27, the lengths of the lines being indicative of signal strength and thus relative range of the detected object, while the inclinations of the lines indicate the azimuth and elevation alignment errors. The indicator circuits each comprise, Fig. 2, two clamping circuits consisting of pairs of valves 31, 32 and 61, 62 in series. The positive triggering pulse fed to the grid input terminal 41 causes the valves to conduct and hold the potentials at points 47 and 66 at steady values. The potential at point 47 is equal to the receiver A.V.C. voltage, which is fed to terminal 45, when no signal is being received. If a signal is received, the voltage across condenser 51 changes exponentially towards the A.V.C. voltage level during the intervals between the triggering pulses while the valves are cut-off, producing the sweep voltage 40 of amplitude proportional to the signal. The error voltage from the azimuth or elevation phase-sensitive detector is fed to terminal 65 and a sweep voltage 60, which is positive- or negative-going in dependence upon the direction of error and of amplitude proportional to the magnitude of the error and the signal strength, is therefore generated across condenser 81 by the potential of point 66 moving towards the applied voltage on terminal 65. These sweep voltages are fed through push-pull amplifiers 34, 64 to the vertical- and horizontal-deflecting, plates of the cathode-ray tube 26 to produce the resultant straight line deflection 92 which is proportional to signal strength, and makes with the vertical an angle #, which is indicative of the azimuth or elevation error and is independent of signal. strength. The indicator circuits may be modified, Fig. 3 (not shown), so that a zeroerror datum line is traced on the screen. The positive triggering pulses fed to terminal 41 are arranged to be of longer duration and are applied to the clamping circuit producing, the vertical deflection through an integrating circuit which so distorts the waveform that the verticaldeflecting saw-tooth is of longer duration than the saw-tooth wave producing the horizontal deflection and continues to produce vertical deflection after the By-back of the horizontal deflection. The positive triggering pulses are fed through a differentiating circuit to blackout the horizontal fly-back. The fly-back of the vertical deflection is not blacked out and completes the trace of the zero-error datum line, a bright spot being produced at zero by the differentiated pulse wave.